1. Field of the Invention
This invention relates to valves, and more particularly to fast acting valves capable of operation under cryogenic conditions.
2. Description of the Prior Art
Valves generally control the flow of material from one place to another, and often provide a seal which restrains the flow of material entirely. Valves are needed which operate under a variety of pressure and temperature oonditions, including cryogenic environments.
In many applications, a valve is needed which opens and closes very rapidly and changes state many times during its useful life. The ability of a valve to meet these requirements may depend upon the number of moving parts in the valve, the manner in which the parts move, the stroke of the actuating mechanism required to change the state of the valve, and the manner in which a particular state of closure is maintained.
Generally, it is preferable for a valve to have a minimum number of moving parts for improved reliability, low cost and long useful life. The manner in which the parts move may be important because under certain temperature and pressure conditions, parts which slide over each other may stick together. Valves which operate in relatively clean environments present additional problems and are particularly susceptible to sticking when parts of the valve rub over each other. Valves having parts which press together without sliding over each other are less likely to stick together in use, and are therefore more reliable.
The valve of the present invention has many uses, and finds particular application in connection with cryogenic pumps operating at very low temperatures and pressures. For such application, it is necessary that impurities in the valve and impurities on the surface of the valve material not contaminate the environment. As all materials will be contaminated initially, it is desirable that it be possible to outgas the contaminants before using the valve. This is ordinarily achieved by baking at high temperatures, ruling out the use of such gasket materials as rubber or plastic in the valve. For this reason, metal to metal seals are preferred in the present invention.
It is also desirable in some applications to construct a valve so that it changes state of closure with a relatively small actuating stroke, and maintains a particular state in the absence of an actuating force. Typical applications for such valves include liquid or gas pipes, storage tanks, internal combustion engines and the like. The actuating stroke may be reduced through mechanical means, and a particular state may be maintained through the use of springs and the like. Added parts are often needed to accomplish these purposes, however, which decreases reliability and may require parts which slide over each other. Thus, there is a need for valves which change state with a relatively small actuating stroke and maintain a particular state in the absence of an external actuating force, with parts which generally press together, without substantial sliding.
Accordingly, one aspect of this invention is to provide a new and improved valve.
Another aspect of this invention is to provide a new and improved fast acting valve which maintains a particular state in the absence of an actuating force, having parts which generally press together without substantial sliding.
Still another aspect is to provide a bow action valve having parts which generally press together withqut sliding, as for use in cryogenic applications.